Conventional reservoirs for use in automotive vehicles, which are referred to as master cylinder reservoirs, include a main body in which is defined a reserving chamber and a pouring opening located adjacent the reserving chamber. The pouring opening is formed at the upper portion of the main body and is positioned at the forward vehicle side of the main body.
To introduce an amount of operating or brake fluid into the reserving chamber, a reservoir cap must first be removed from the pouring opening and the operating fluid is then supplied in the reserving chamber through the pouring opening. The pouring opening is then once again closed by the reservoir cap. The reserving chamber is in fluid communication with the pouring opening, and the reservoir cap which closes the pouring opening is formed with a vent hole for introducing atmospheric air into the reserving chamber so that the reserving chamber is under atmospheric pressure.
In this type of reservoir, when the brake is applied during forward movement of the vehicle, the upper surface of the operating fluid becomes inclined such that the operating fluid surface extends diagonally upward in the forward vehicle direction. It has been found that when the upper surface of the fluid experiences this type of inclination, if the distance between the fluid surface and the pouring opening is insufficient, leakage of the operating fluid outside the reservoir through the vent hole inevitably occurs. Such leakage of the operating fluid is, of course, highly undesirable,